Share
Explore BrainMass

Organic Reaction Intermediates and Mechanisms

In an Organic Reaction Mechanism, a Reaction Intermediate is a molecular entity that is formed by the reactants which reacts further to form the products. Although, there are a multitude of organic reactions with multiple mechanisms and intermediates, there are a few reaction mechanisms which form the foundations of organic reactions. One of these is the Nucleophilic Substitution Reaction which involves an electron nucleophile attacking a positively charged atom (which is usually a carbon) in order to substitute a leaving group. These reactions can be broken down into two further categories: SN1 and SN2.

SN1 reactions are substitution reactions where the rate-determining step is unimolecular. This suggests that the mechanism is only dependent on the electrophile, and totally independent of the nucleophile. Knowing these details, it can be inferred that the intermediate that forms in the reaction, if the electrophile is carbon-based, is a carbocation.  After the carbocation forms, then the nucleophile will subsequently attack it based on the opposition of charge. Thus the leaving group was replaced by a nucleophile – hence the term SN1 (unimolecular nucleophilic substitution reaction).

SN2 reactions are also substitution reaction, but with a different reaction mechanism, as it proceeds in a bimolecular manner. The nucleophile in this case attacks the electrophile without a leaving group leaving. Thus, a temporary transition state with five substituents around the carbon is formed. Eventually, the leaving group leaves and the structure around the central carbon inverses.

Although nucleophilic substitution reactions are prevalent in Organic Chemistry, there are other important reactions such as Elimination Reactions, which may share some of the reaction mechanisms and intermediates, such as the carbocations. Thus, in Organic Chemistry, it is most often the physical and chemical conditions which determine which intermediates form as well as the direction of a particular reaction.

TLC Analysis of Midol

A student obtained a silica gel TLC plat shown in attached figure by spotting samples of Midol, caffeine and acetaminophen on the plate, then eluting with petroleum ether: chloroform What are the Rf-values of acetaminophen and caffeine, respectively? Based on this TLC analysis, what are the ingredients in a tablet of Midol? W

Chromatography: Benzoic Acid and Aniline

1. Benzoic acid is soluble in diethyl ether but not water; however, benzoic acid is extracted from diethyl ether with aqueous sodium hydroxide. Complete the acid-base reaction below by writing the products of the reaction and label the acid, the base, the conjugate acid and the conjugate base. The diagram attached below.

The Order of Elution in Column Chromatography

In normal phase column chromatography, which solvent has more eluting power: petroleum ether or dicloromethane? In what way is the eluting power of a solvent related to its polarity? In normal phase column chromatography, how does the principle of like dissolve like explain the affinity of a compound for the mobile phase, relati

Chemistry

Naphtalene is soluble in diethyl ether, but it is insoluble in water regardless of the solution pH. Explain why this compound cannot be readily ionized in aqueous solution. There are three common functional group in organic chemistry that are readily ionized by adjusting the pH of the aqueous solution during an extraction. Na

Reactions of Carbonyl Compounds

See attachment for better symbol and reaction representation. 1. Complete the following reaction by drawing a structural formula for the product. ? • You do not have to consider stereochemistry. • You do not have to explicitly draw H atoms. 2. Draw a structural formula for the major organic anion formed when

Separating Catenated Circular DNA Complexes

Two circular DNA duplexes are catenated, or captured as interlocking rings. Draw a general mechanism that shows how these could be resolved into two free circles. You don't need to draw individual base pairs or a precise chemical mechanism of esterification by an active site tyrosine, but you do need to demonstrate generally how

Organic Halogen Compounds

I am requesting help with the following questions. If possible please format in a Word Document: 1. Tell what products you expect and by what mechanism they are formed for each of the following reactions: a. 2-chlorohexane + ethanol b. 2-chlorohexane + sodium ethoxide (in ethanol) c. 2-chlorohexane + sodium hydrosulfi

Structures and Natural Products

11. Refer to Exhibit 9-7. Two structures have been proposed for this natural product. Circle the structure that is consistent with the information presented and briefly explain your choice. 12. Draw a structure for a singly substituted chiral chloroalkane that contains four carbon atoms with R stereochemistry. Indicate the c

Organic Halogen Compounds

Select an alkyl halide and a nucleophile that will give each of the following products: Please refer to the attachment for full questions.

Elimination and Substitution

Your given a cyclohexane ring with a dashed Chlorine at C1 and a wedged methyl at C1, also there is wedged methyl at C2 and C6. Thus making there no trans protons available on these carbons for elimination (except methyl connected to chiral carbon w/chlorine, I think) the questions requires you to determine Substitution products

Oraganic Chemistry: Reaction Mechanisms

* What would happen to the rate of Sn2 reaction if the solvent was changed from acetone to water? * How do E1 and E2 mechanisms depend on the properties of a base? * What is the difference between polar protic solvent and polar aprotic solvents and how do they determine if a reaction is going to be sn1, sn2,E1 or E2

DDT and its Effect on Peregrine Falcon Eggshells

The banned pesticide DDT has been identified as the cause of thin egg shells produced by Peregrine falcons. What chemical process did DDT disrupt? Explain your answer. Response needs to be in 200-300 word essay form.

Aldol Addition Reaction Mechanism

Which one of the following best represents the flow of electrons in the key step for the aldol addition reaction that occurs when propanal is treated with sodium hydroxide?

Ester synthesis and reaction problems

Please see the attached file. 1. Consider the reaction sequence below to answer the following questions: Compound X, diethyl propanedioate, is more commonly known as_____. 2. Consider the reaction sequence below to answer the following questions: The starting material A in this reaction sequence is called a __

Synthetic Pathway for Synthesis of 4-bromoacetanilide

Provide a reasonable synthetic pathway for the synthesis of 4-bromoacetanilide starting from benzene. Show the reagents necessary to accomplish each step and the structure of the intermediate products. Show only the reagents, not the mechanism. See attached file for full problem description.

Glucose

2. Turn the -OH on carbon 5 around so it is close to the aldehyde carbon (carbon #1). 3. Form the hemi-acetal using the carbon #5 -OH and the carbonyl at carbon 1. a. As you make the hemi-acetal, write out the mechanism by which this occurs. Concentrate your efforts on what is happening at C5 and C1. Review the formation of

Aldol Condensation Reaction

Could you please give a stepwise mechanism for the preparation of 3-nitrochalcone from 3-nitrobenzaldehyde and acetophenone. (This is an aldol condensation reaction)

Synthetic schemne for synthesis

(See attached file for full problem description) Complete the attached synthetic scheme by providing the reagents required for synthesis

Aldol Condensation Production of Pentaerythritol

I am stumped by a question from my textbook. The question reads: the compound pentaerythritol C(CH2OH)4 used in making explosives, is obtained from the reaction of acetalaldehyde and formaldehyde in the presence of Ca(OH)2. outline the probable steps in the structure. --- I think I know the final outcome I am having trouble with

NMR Spectral Data

With NMR spectral data supplied I need to know the structure of product X and structure of product Y as well as mechanism by which product X is formed. (See attached file for full problem description)

Products of Organic Chemistry Reactions

I need help with showing the products for the following attached reactions problem. Please see attachment. Show the product(s) of the following reactions. Show stereochemistry where applicable.